Difference between WPA1-PSK CCMP and WPA2-PSK CCMP

Bryan Kadzban bryan at kadzban.is-a-geek.net
Mon Aug 28 12:47:11 EDT 2006


On Tue, Aug 29, 2006 at 01:13:48AM +1000, Nicholas Chan wrote:
> Hi i noticed in wpa_supplicant, you have a choice between wpa1-psk
> ccmp and wpa2-psk ccmp.
> 
> I was wonder what is the difference between them? From the 802.11i
> standard, it states that wpa1-psk uses TKIP whereas wpa2-psk uses
> CCMP.

Both WPA1 and WPA2 can use either TKIP or CCMP encryption.  (It is true
that some APs and some clients restrict the combinations, but there are
four possible combinations, and AFAIK all of them are Wi-Fi Alliance
standards.  WPA1 with CCMP may not be, but I believe it is.)

The difference between WPA1 and WPA2 is in the information elements that
get put into the beacons, association frames, and 4-way handshake
frames.  The data in these IEs is basically the same, but the identifier
used is different.  WPA1 uses (one of?) Microsoft's OUI(s) along with an
ID byte or two that Microsoft guarantees is unique as its IE identifier,
while WPA2 uses an IE identifier that the IEEE assigned as part of the
802.11i standard.

So there is a difference, and both supplicants and APs have to
understand the WPA2 IE identifier values to be able to work in WPA2
mode.  But the actual behaviors (the key exchange, and the encryption
and decryption processes) are the same in both modes.

> Or did i missed out something from the standard?

I'm not sure if it's in the standard or not (I'd assume it is somewhere,
but I don't know for sure), but I noticed the difference while doing
some wireless captures of the association process on WPA1 and WPA2
networks.  Ethereal (yes, yes, it's now called Wireshark, but it was
Ethereal at the time) was able to decode the various IEs, and I noticed
that the IE identifiers were different depending on the network mode.

Actually, the difference may only show up if you compare the Wi-Fi
Alliance standards for WPA1 and WPA2.  IIRC, the IEEE standard doesn't
mention WPA1 at all.

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